It's a Girl for Jamie Lynn

Around 9:30 a.m. on June 19, the soothing melody of Brahms' "Lullaby" filled the corridors of the maternity ward at Southwest Mississippi Regional Medical Center in McComb, Miss., as it does every time a baby is born there. But never before had it heralded the arrival of such a mini-celebrity as Maddie Briann, the 7-lb., 11-oz. first child of Nickelodeon star Jamie Lynn Spears, 17, and her fiancé, Casey Aldridge, 19. The "long" little girl, says a source close to the couple, was born with a full head of hair and what new grandma Joyce Aldridge observed to be "Casey's toes." Adds the source: "They're doing terrific."

For the Spears family, who have weathered a tumultuous seven months (the shock of the teen's pregnancy news; sister Britney's breakdown), the birth was a rare, joyful occasion. "This baby could be a turning point in the family," a Spears family friend tells PEOPLE. "For once, everyone was together and was happy."

The reunion began on June 18, when Britney, 26, brother Bryan, 31, and dad Jamie, 56, arrived from L.A. and connected with mom Lynne, 53, who has been in their hometown of Kentwood, La., since mid-May. For Britney—who lost custody of her two sons to ex-husband Kevin Federline in January and now sees them three times a week—becoming an aunt is bittersweet, says the family friend: "She's happy about Jamie Lynn, but it only reminds her of her own mistakes. It was a big step for her to come back."

The group spent their first evening in the area at Jamie Lynn and Casey's new home in Liberty, Miss. The mood was upbeat and "low-key," says the Spears family friend, noting, "They have had nine months to deal with this." The next day the couple arrived at the hospital around 4 a.m.—about two hours before Spears was induced—and settled into a private maternity suite. The delivery didn't take long: "Just two pushes and [Maddie] was out," says a family insider. Afterward, Aldridge's parents, his sister and the Spears clan joined the new parents in the birthing room and took turns holding Maddie.

News of the birth brought a mix of excitement and concern among friends and relatives. "I wish her the best," says distant Spears cousin Margie Busby. "But she's got probably a hard road, with her so young and a baby." Judy Cambre, a secretary in Liberty who knows the couple, tells PEOPLE, "I think [Casey's] going to make a good father and she's going to be a wonderful mama."

Indeed, over the past nine months, the former Zoey 101 star has shown signs of maturity: earning her GED, getting engaged to Aldridge, shopping for the baby and decorating their home. "She's taking full responsibility for her own life, making good choices and good decisions," says a source. According to the family friend, Jamie even told Jamie Lynn "it's her turn to be the example" to her older sister.

Due to Britney's own maternal responsibilities, the family reunion was short-lived. Just a day after Maddie's birth, Jamie and Britney flew back to L.A.; the next morning her kids Preston, 2, and Jayden, 1, arrived for their usual Saturday visit. But the Spearses may have reason to reunite again soon, for Jamie Lynn and Casey's wedding, though the date hasn't been set. As for when the new mom might return to Hollywood, that too is uncertain. "I understand she plans to go back to work," says a source, "but I don't think she's in any rush. They have a lot to deal with right now."